1. Field of the Invention
The invention relates to devices and methods for detecting user input, and more particularly, to an input device comprising a multi-touch sensing display.
2. Related Art
Modern electronic devices often use a plurality of control elements to allow a user to adjust parameters relevant to the operation of the device. An example of an input unit that may be used in an electronic device includes a console having a plurality of mechanical control elements. Such an input device may be used to control, for example, audio equipment, video equipment, or a central control station including, for example, a power plant, a factory, or a traffic system. Control elements employed in these systems include analog input elements.
Analog input elements have a predefined function. Their function cannot be changed or adjusted once implemented limiting their application in the input unit. Control elements that operate using encoders, such as for example, rotary encoders, are programmable as to their, function. However, in operation, it may be difficult or even impossible to determine the function that is assigned to the control element at any given time. It is even more difficult if the function and value of an associated parameter is displayed on a separate screen remote from the control element. Control elements that use encoders and other complex electromechanical input elements also tend to be relatively expensive and overly complex. Input units that use such electromechanical input elements must typically accommodate a fair amount of space underneath the cover plate of the input device, further adding to their cost and making them difficult to mount. Cost, expense and mounting difficulty present substantial problems for large input consoles that may include up to tens or hundreds of control elements.
Touchscreens are input devices often implemented in compact electronic devices, such as personal digital assistant (PDA) or more recently mobile phones. Touchscreens may use one of several known technologies for detecting a touch or a near-touch to a surface. One example includes a resistive touchscreen panel composed of several layers. When the panel is touched, a change in the electrical current through the layers may be detected as a touch event. A controller may derive the position of the touch event on the panel based on the change in current, which is different at any given position. Other touchscreen technologies include capacitive touchscreen panels based on detecting a distortion of an electromagnetic field, or frustrated total internal reflection (FTIR). Some FTIR touchscreen panels use reflected light paths in which a reflection light path internal to a glass plate provides a sensitive surface. A disturbance to the light path may be detected by pressing an object against the surface. These touchscreens can be operated with objects like a finger or a pen. Some touchscreen panels may trigger input events upon a near touch. For example, a capacitive touchscreen may trigger an input event if an object comes to within a predetermined distance of the touchscreen surface.
Touchscreens were originally designed to detect a single touch at a time. Touchscreens have since evolved to detect simultaneous multiple touches as separate input events. Such multi-touch screens allow a user to use two or more fingers to simultaneously manipulate two or more objects. Despite their flexibility, multi-touch screens are not well-suited for applications involving setting a larger number of parameters. The screens are generally small in size and operated by one hand. The adjustment of a graphical control element on the touchscreen using for example a finger or a pen may demand substantial motor skills from a user and yet, still be rather imprecise. A graphical control element typically requires a substantial amount of space on the screen limiting the number of such elements displayed at any given time. A plurality of small control elements would be difficult and time-consuming to operate. Adjusting a plurality of parameters with a conventional touchscreen is thus not ergonomic, particularly if such adjustments are to be performed over a prolonged time.
Accordingly, there is a need for an ergonomic input device that allows for flexible precise adjustment of parameters and that informs a user of the parameter being adjusted.